Actress Kristin Scott Thomas told how “two brains were better than one” as she and her stage co-star exchanged tips on the roles they are set to share in London for the next 12 weeks.

Scott Thomas and Lia Williams are taking it in turns to play the two female characters Kate and Anna in 'Old Times', a play by Harold Pinter and the first to be performed in the Comedy Theatre since it was re-named after him.

Paris-based Scott Thomas, 52, said: “There are two brains working on the same part. I absorb everything Lia does and take note. You’re both pinching each other’s ideas. It’s very exciting. I love the dynamic between the women — female friendship and love, the way one tries to steal the other one’s life.”

But Williams, 48, is not complacent at the prospect of swapping roles after every three performances — and on the toss of a coin once a week. “It’s terrifying but thrilling at the same time and such a good acting challenge,” she said.

The play reunites Williams with Rufus Sewell, 45, for the first time since they starred in the film Dirty Weekend, by the late Michael Winner, 20 years ago.

Sewell felt the role-swapping added “edge”, saying: “The normal rehearsal process is building up little ideas and moments till you have a performance. But we would do that and then they would swap and my little moments would no longer apply.”

Scott Thomas revealed after last night’s opening that she does intend to return to Britain for good, saying: “I won’t straight away but I will one day.”

Both she and Williams have performed Pinter in the same theatre before. “You can feel Harold here,” said Williams. The playwright’s widow Lady Antonia Fraser met the cast after last night’s show — which was a unanimous hit with theatre-goers.

Theatre production apprentice Sarah Brown, 23, of East Dulwich, said: “I want to see it again with the women’s roles swapped around.”

Production assistant Lydia Rynne, 25, of Bethnal Green, said: “I was gripped the whole way through and now afterwards I’m anxious to work it all out.”

Merchandiser Jeffrey Marshek, 38, of Covent Garden, said: “All three actors were fantastic. It was really such hard material to pull off.”